Y. Mizumoto

Evidence for 500 TeV gamma-ray emission from Hercules X-1

A signal (chance probability = 2 x 10/sup -4/) with a 1.24 s period has been observed from the direction of Hercules H-1. The signals relatively long period and high shower energy conflict with some popular models of particle acceleration by pulsars. Optical and X-ray data support our picture in which energetic particles produce multi--TeV ..gamma..-rays by collisions with Hercules X-1s accretion disk.

Limits on astrophysical. nu. /sub e/ flux at E/sub. nu. />10/sup 19/ eV

We report on a search for upward-going extensive air showers using the University of Utah Flys Eye detector. No eVents hae been found in 3.9 x 10/sup 6/ s of running time. The resultant ..nu.. flux limit at 10/sup 20/ eV varies from 5.8 x 10/sup -16/ ..nu.. cm/sup -2/ s/sup -1/-sr/sup -1/ to 3.0 x 10/sup -14/ ..nu.. cm/sup -2/ s/sup -1/ sr/sup -1/ for sigma/sub ..nu../ between 10/sup -33/ cm/sup 2/ and 10/sup -3/ cm/sup 2/. We also present flux limits for large sigma/sub ..nu../ using near-horizontal events originating in the atmosphere. The implications of the flux limit at E/sub ..nu../>10/sup 20/ ev are discussed.

Upper limits for northern hemisphere 10 V eV gamma-ray sources

Flux limits in the range 10 T to 10 S cm S s have been obtained by observing Cerenkov flashes from small air showers. Simultaneous drift scans by the 67 mirror units of the Utah Flys Eye gave nearly full coverage of the Northern Hemisphere. During 1983, a 3.5 sigma excess of showers was observed during the phase interval 0.2--0.3 of the 4.8 hr period of Cygnus X--3, but no excess was found in 1984 observations.

Limits on the ≳1017 eV cosmic ray νe flux

We report on a search for upward‐going extensive aire showers using the University of Utah Fly’s Eye detector. No event have been found in 6×106s of running time. The resultant νe flux limit for σν=10−33 cm2 varies from 7.2×10−14 to 5.0×10−17 ν/cm2‐sec‐ster for Eν between 1018 and 1021 eV. We also present limits for larger σν using near‐horizontal events originating in the atmosphere.

Measurement of the angular distribution of Cerenkov light in ultra-high-energy extensive air showers

The authors report on a direct measurement of the angular distribution of Cerenkov light in extensive air showers with energies greater than 1017 eV. The measurement is performed by viewing sections of showers simultaneously at different emission angles with two Flys Eye detectors. The data imply a value of the multiple scattering parameter theta 0=4.0+or-1.2 degrees for threshold energies between 20 and 60 MeV.

The Fly’s eye

We describe a high energy physics observatory, the Fly’s Eye, designed to measure extensive air showers (EAS) in the energy range 1017–1021 eV via atmospheric fluorescence. Preliminary results are presented for the following measurements: (1) the high energy cosmic ray spectrum at 1017–1019 eV, (2) the total proton cross section σpp, (3) limits on the extra‐galactic neutrino flux at 1020 eV.